The present invention relates to a V-type internal-combustion engine, and more particularly, to the type of engine in which there are two banks of cylinders, each with a cylinder-head housing which is covered by a cylinder-head cover, and, on each end face, by an end cover and in which is arranged in at least one camshaft driven via a respective chain wheel and a common chain by a crankshaft. Between the banks of cylinders, in the region of the cylinder heads and cylinder-head covers, a free space is sealed off relative thereto and through which the chain is led in a well between the banks which is formed by a well housing sealing off from the free space.
An internal-combustion engine is shown in DE-Z MTZ 48 (1987), pages 315 to 323, in which the well is located in the region of the parting planes between the cylinder-head housings and cylinder-head covers of the two banks of cylinders. This arrangement raises considerable difficulties with regard to sealing because there is a plurality of intersecting sealing surfaces.
An object on which the present invention is based is to provide an internal-combustion engine in which the sealing difficulties arising as a result of the lead-through of the chain between the two banks of cylinders are considerably reduced.
In the above-mentioned type of internal-combustion engine, this object has been achieved by arranging the well housing at a distance from the parting planes between the cylinder-head housings and the cylinder-head covers and fastening the well housing solely between the cylinder-head housings and the end covers.
In an internal-combustion engine constructed in accordance with the principles of the present invention, the well housing forms parting planes to be sealed off only relative to the cylinder-head housings, and associated end cover, while there are no intersections with the parting planes between the cylinder-head housings and the cylinder-head covers. The possible number of jumps of sealing surfaces which are especially difficult to seal off is also consequently smaller, and therefore fewer sealing problems arise overall. The appropriate position of the chain within a cylinder head can be obtained in a simple way, for example by the deflection of the chain by way of a deflecting gearwheel which can also be formed by the chain wheel for a second camshaft in the respective bank of cylinders under which the chain is led through.
One embodiment of the present invention constitutes a substantial simplification of the well housing in relation to known arrangements in which the well covers extend simultaneously over the end faces of the two cylinder heads and cylinder-head covers. This known structure is disadvantageous in that these covers have low rigidity because of their size and are difficult to handle where machining, transport and assembly are concerned. Furthermore, the unavoidably large tolerances between the banks of cylinders necessitate further intermediate covers, via which tolerances between the well covers and auxiliary units, such as an ignition distributor, guided therein, driven by a camshaft and necessarily aligned there with have to be compensated. In contrast, the well covers according to the one embodiment of the present invention are very easy to handle because of their small dimensions. Tolerances existing between the banks of cylinders can easily be bridged thereby and have no detrimental influence on the fastening of auxiliary units to the camshafts. This is due to the face that the end cover, which is separate for each bank of cylinders and in which the auxiliary units are guided, can be readily fastened to the associated cylinder head with the necessarily narrow tolerance in relation to the driving camshaft.
Another feature of the present invention beneficially solves the principle sealing problem remaining in the region of the junction of the rear and front well cover and the two end covers. The local conjunction of three parts to be sealed off relative to one another, where the sealing is especially difficult because of the possible occurrence of jumps in the sealing run, is simplified by embedding the front well cover into a sealing element to form a more easily sealed junction of two parts to be sealed off relative to one another (namely, a well cover and a respective end cover) and of a sealing element. Also, this embodiment ensures the fastening of the front well cover simultaneously with the sealing and without any further outlay.
A still further feature of the present invention provides the seals between the rear well cover and the two end covers as part of the sealing element. The front well cover is embedded therein, so that, with the joining together of the two well covers, the sealing strips also assume their correct location. Moreover, this one-part configuration avoids a joint between the sealing element and the seals between the rear well cover and the end covers, which could result in leaks.
Another feature of the present invention guarantees the correct position of the sealing strips in the longitudinal direction of the well by arranging the longitudinal recesses, into which the sealing strips engage, in the rear well cover.
By providing the sealing strips with noses at the free ends thereof so as to face away from the rear wheel cover, the end covers, when being attached, can press the ends of the sealing strips more easily against the rear well cover and take them along in the direction of the cylinder-head housing.
The danger that the sealing strip will be damaged when the end covers are attached is reduced in accordance with the present invention by virtue of the sealing surfaces between the rear wheel cover and the end covers extending obliquely apart from one another towards the cylinder head housings.
Without a separate support for the rail having to be provided, the use of well housing to form a rail support ensures a guidance of the chain in the well and an increase of the looping angle of the chain wheels located nearest to the well.
The present invention ensures that tolerances existing between the cylinder-head housings of the two banks of cylinders have an effect solely in the longitudinal direction of the well between the well covers, on one hand, and the individual end covers, on the other hand, which tolerances are easy to control in sealing terms, whereas they have virtually no effect in the transverse direction of the well. A simply produced tolerance compensation configuration can be provided by a long hole in the second cylinder-head housing, with a longitudinal extension in the longitudinal direction of the well with fitting surfaces in transverse direction of the well.